1. Field of the Invention
2. Description of the Prior Art
As oil supplies continue to deplete, the ability to recover additional oil from existing and/or abandoned well sites or formations becomes of greater importance. One method for recovering additional oil and gas from a formation is to create holes or perforations which extend horizontally away from the borehole and into the formation.
There are tools in the industry capable of forming horizontal bores or holes. These can generally be categorized as (1) hydraulic or (2) flexible shaft tools. As shown in U.S. Pat. No. 4,317,492 (Summers), U.S. Pat. No. 5,439,066 (Gipson) and U.S. Pat. No. 5,853,056 (Landers), U.S. Pat. No. 5,934,390 (Uthe), hydraulic fluid can be used to create holes or perforations in oil bearing formations. Typically a hose or tube is passed down the exiting well bore to a point where the horizontal bore is desired. The hose extends from the surface, where a pump provides pressurized hydraulic fluid, such as water, to erode the rock or sand surrounding the downhole end of the hose. While somewhat effective in forming holes in the strata surrounding the main bore, this method significantly damages the formation, which may hinder additional oil or gas production.
Many tools, such as that shown in U.S. Pat. No. 4,226,288 (Collin), as well as those shown in the '056 and '066 patents, provides a flexible shaft which extends from the surface, down the main bore and then turns or bends to extend horizontally into the formation, traveling generally perpendicular to the main bore. While these tools may be suitable for use in very large well bores, they are not suitable for use in wells having smaller bores because the turning radius of the flexible shaft is too great. Additionally, those tools which turn the entire shaft to provide rotation of a drill bit do not typically travel perpendicular to the well bore. The rotation of the shaft creates a downward spiraling of the drill bit.